/**
 * @option_param {dom} target dom对象
 * @option_param {int} startVal 开始数字
 * @option_param {int} endVal 结束数字
 * @option_param {int} decimals 小数位数 
 * @option_param {int} duration 持续时间 单位-秒
 */
(function(root, factory) {
	if (typeof define === 'function' && define.amd) {
		define(factory);
	} else if (typeof exports === 'object') {
		module.exports = factory(require, exports, module);
	} else {
		root.countUp = factory();
	}
}(this, function(require, exports, module) {
	var CountUp = function(target, startVal, endVal, decimals, duration, options) {
		var lastTime = 0;
		var vendors = ['webkit', 'moz', 'ms', 'o'];
		for (var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) {
			window.requestAnimationFrame = window[vendors[x] + 'RequestAnimationFrame'];
			window.cancelAnimationFrame =
				window[vendors[x] + 'CancelAnimationFrame'] || window[vendors[x] + 'CancelRequestAnimationFrame'];
		}
		if (!window.requestAnimationFrame) {
			window.requestAnimationFrame = function(callback, element) {
				var currTime = new Date().getTime();
				var timeToCall = Math.max(0, 16 - (currTime - lastTime));
				var id = window.setTimeout(function() {
						callback(currTime + timeToCall);
					},
					timeToCall);
				lastTime = currTime + timeToCall;
				return id;
			};
		}
		if (!window.cancelAnimationFrame) {
			window.cancelAnimationFrame = function(id) {
				clearTimeout(id);
			};
		}

		// default options
		this.options = {
			useEasing: true, // toggle easing
			useGrouping: true, // 1,000,000 vs 1000000
			separator: ',', // character to use as a separator
			decimal: '.' // character to use as a decimal
		};
		// extend default options with passed options object
		for (var key in options) {
			if (options.hasOwnProperty(key)) {
				this.options[key] = options[key];
			}
		}
		if (this.options.separator === '') this.options.useGrouping = false;
		if (!this.options.prefix) this.options.prefix = '';
		if (!this.options.suffix) this.options.suffix = '';

		this.d = (typeof target === 'string') ? document.getElementById(target) : target;
		this.startVal = Number(startVal);
		this.endVal = Number(endVal);
		this.countDown = (this.startVal > this.endVal);
		this.frameVal = this.startVal;
		this.decimals = Math.max(0, decimals || 0);
		this.dec = Math.pow(10, this.decimals);
		this.duration = Number(duration) * 1000 || 2000;
		var self = this;

		this.version = function() {
			return '1.6.0';
		};

		// Print value to target
		this.printValue = function(value) {
			var result = (!isNaN(value)) ? self.formatNumber(value) : '--';
			if (self.d.tagName == 'INPUT') {
				this.d.value = result;
			} else if (self.d.tagName == 'text' || self.d.tagName == 'tspan') {
				this.d.textContent = result;
			} else {
				this.d.innerHTML = result;
			}
		};

		// Robert Penner's easeOutExpo
		this.easeOutExpo = function(t, b, c, d) {
			return c * (-Math.pow(2, -10 * t / d) + 1) * 1024 / 1023 + b;
		};
		this.count = function(timestamp) {

			if (!self.startTime) self.startTime = timestamp;

			self.timestamp = timestamp;

			var progress = timestamp - self.startTime;
			self.remaining = self.duration - progress;

			// to ease or not to ease
			if (self.options.useEasing) {
				if (self.countDown) {
					self.frameVal = self.startVal - self.easeOutExpo(progress, 0, self.startVal - self.endVal, self.duration);
				} else {
					self.frameVal = self.easeOutExpo(progress, self.startVal, self.endVal - self.startVal, self.duration);
				}
			} else {
				if (self.countDown) {
					self.frameVal = self.startVal - ((self.startVal - self.endVal) * (progress / self.duration));
				} else {
					self.frameVal = self.startVal + (self.endVal - self.startVal) * (progress / self.duration);
				}
			}

			// don't go past endVal since progress can exceed duration in the last frame
			if (self.countDown) {
				self.frameVal = (self.frameVal < self.endVal) ? self.endVal : self.frameVal;
			} else {
				self.frameVal = (self.frameVal > self.endVal) ? self.endVal : self.frameVal;
			}

			// decimal
			self.frameVal = Math.round(self.frameVal * self.dec) / self.dec;

			// format and print value
			self.printValue(self.frameVal);

			// whether to continue
			if (progress < self.duration) {
				self.rAF = requestAnimationFrame(self.count);
			} else {
				if (self.callback) self.callback();
			}
		};
		// start your animation
		this.start = function(callback) {
			self.callback = callback;
			self.rAF = requestAnimationFrame(self.count);
			return false;
		};
		// toggles pause/resume animation
		this.pauseResume = function() {
			if (!self.paused) {
				self.paused = true;
				cancelAnimationFrame(self.rAF);
			} else {
				self.paused = false;
				delete self.startTime;
				self.duration = self.remaining;
				self.startVal = self.frameVal;
				requestAnimationFrame(self.count);
			}
		};
		// reset to startVal so animation can be run again
		this.reset = function() {
			self.paused = false;
			delete self.startTime;
			self.startVal = startVal;
			cancelAnimationFrame(self.rAF);
			self.printValue(self.startVal);
		};
		// pass a new endVal and start animation
		this.update = function(newEndVal) {
			cancelAnimationFrame(self.rAF);
			self.paused = false;
			delete self.startTime;
			self.startVal = self.frameVal;
			self.endVal = Number(newEndVal);
			self.countDown = (self.startVal > self.endVal);
			self.rAF = requestAnimationFrame(self.count);
		};
		this.formatNumber = function(nStr) {
			nStr = nStr.toFixed(self.decimals);
			nStr += '';
			var x, x1, x2, rgx;
			x = nStr.split('.');
			x1 = x[0];
			x2 = x.length > 1 ? self.options.decimal + x[1] : '';
			rgx = /(\d+)(\d{3})/;
			if (self.options.useGrouping) {
				while (rgx.test(x1)) {
					x1 = x1.replace(rgx, '$1' + self.options.separator + '$2');
				}
			}
			return self.options.prefix + x1 + x2 + self.options.suffix;
		};

		// format startVal on initialization
		self.printValue(self.startVal);
	};

	return CountUp;

}));